Flexible endoscopes are well known and commonly are provided with a flexible shaft capable of being advanced past corners to investigate deep body cavities. An endoscope commonly has a fiber optic light carrier and viewer whereby a physician may inspect the body cavity. The fiber optics is flexible and is located in a duct of the flexible shaft to terminate with suitable viewing optics at a distal tip of the shaft. Other endoscope tubular ducts are provided through which, for example, a liquid can be passed such as water and a surgical tool may be employed to conduct a surgical procedure under view with the aid of the flexible fiber optics.
The surgical tools available for use through an endoscope duct vary depending upon the particular procedure being used or the physiological problem being investigated. In one tool, for example, a measuring device is provided, which is straight as it is passed through an endoscope duct, but when it emerges at the tip resumes a particular shape adapted to, for example, measure tumors with the aid of visible graduations.
In another surgical tool a conductive snare is located at the end of a long line and inserted in a long catheter. The snare is controlled with a handle at a proximal end of the endoscope from where the snare's protrusion at the distal end of the catheter and electrical cutting action is controlled. Other surgical tools may be forceps, scissors, needles, brushes with various shapes adapted often for a particular purpose.
For example, one type of surgical tool known as a papillotome is designed to perform a complex surgical procedure involving an investigation of the duodenum, the portion of the alimentary canal immediately downstream of the stomach and a radiographic investigation of the billiary or common duct leading to the pancreas and gall bladder. The common duct terminates in a valve, the ampulla of Vater, or papilla.
If the investigation indicates the presence of stones in the common duct, the condition may be relieved by opening an orifice into the duodenum wall portion which is common with the common duct to let the stones escape. This orifice can be made by cutting with high frequency techniques.
In practice, a duodenoscope is maneuvered until the ampulla of Vater is observed. A catheter is extended from the distal tip and manipulated into the common duct. Once the catheter is inside, a radio-opaque material is fed through the catheter to investigate the duct for obstructions or growths with a radiogram.
In many cases the observation of an obstruction such as a gall stone can be immediately treated by use of an electric or high frequency knife integrally associated with the catheter whose distal end is now inside the common duct. The cutting action usually proceeds from a blind or invisible position of the catheter as it is advanced or withdrawn from the common duct, to thus open the wall between the common duct and the duodenum and enable the discharge of blocking materials.
With one such catheter knife a wire is used inside the catheter lumen and is passed through a side opening near the distal catheter end to lie externally along the end portion of the catheter to its tip to which the wire is anchored. When the wire is retracted, it forms a chord and as the wire is electrified, cuts a slit. A disadvantage of this type of papillotomy knife, or electrode as it may also be called, is that the length of the cut depends upon the length of the chord, which in turn changes with different chord tensions. Since the chord tension changes rapidly as a cut is made, precise control over the length of the cut is difficult at best and more so when one considers the backlash involved in the retraction and extension of the wire.
In another catheter knife an end portion of an electric wire is passed outside of the catheter lumen for a small distance to an anchor point located a short distance from the catheter distal tip. A knife is formed by advancing the wire into the lumen thus forming a hump of the end portion. This type of knife provides poor control with danger to adjacent structures during cutting.